56 THE ORIGIN OF LIFE 



wall ; but in the elementary types which we are 

 now considering, the precise nature of this boundary 

 or even its presence cannot easily be discussed, 

 if it can be discussed at all, for the simple reason 

 that the bodies considered are too minute to come 

 within our range of vision. Wiesmann encounters a 

 similar difficulty, and doubts if spontaneous generation 

 can ever be proved on account of the ultra-microscopic 

 nature of elementary life. Is this cell-wall actually 

 necessary, as a sharply defined boundary, or is it 

 sufficient that it should be merely an envelope 

 surrounding the minute body as an aether envelope 

 is supposed to surround the atom ? Within this 

 ill-defined region like an atmosphere round the 

 atom or particle, the diffusion somewhat similar, 

 though not the same, as that which occurs in the 

 more developed cell-wall of the higher organisms 

 may be taking place. 



Something similar to osmotic pressure, the result 

 of the unequal diffusion of a liquid and a salt 

 through what is called a semi-permeable membrane, 

 may, or may not, be a factor in these elementary 

 types of life. In other words the body may not 

 assimilate from its surroundings and at the same 

 time give to it. The diffusion may be all in the one 

 direction, outwards, without any inward assimilation 

 whatsoever, in the case of any particular particle at 

 any particular time. There would in that case be a 

 pressure outwards, as the diffusion is all that way. 

 Where there is metabolism, however, there would be 

 a building up as well as breaking down of aggregates, 

 whether molecules, chemical atoms, or electrons. And 



